Chapter 20, Problem 6STP

Interpretation Introduction

Interpretation: The reducing agent in the given reaction is to be chosen from the given options.

Concept Introduction:

The chemical process in which both oxidation and reduction take place is called the redox reaction. During this process, an element that donates electrons and undergoes oxidation is called the reducing agent. And, the element which accepts electrons and undergoes reduction is called oxidizing agents.

Answer to Problem 6STP

Correct answer: The correct option is ‘A’.

Explanation of Solution

Reason for correct option: The given reaction is:

  ${\text{MnO}}_4{}^{-}{\text{+SO}}_2^{}\to {\text{Mn}}^{2+}+{\text{SO}}_4^{2-}$

In this reaction, ${\text{SO}}_{\text{2}}$ donates electrons to give ${\text{SO}}_4^{2-}$ and undergo oxidation, therefore, it is the reducing agent.

Half reaction equation:

  ${\text{SO}}_2+{\text{2H}}_2\text{O}\to {\text{SO}}_4^{2-}+{\text{4H}}^{+}$

Conclusion

Reasons for incorrect options:

Option B is incorrect: ${\text{SO}}_4^{2-}$ is the product of ${\text{SO}}_{\text{2}}$ oxidation reaction.

Option C is incorrect: ${\text{Mn}}^{2+}$ is the product of ${\text{MnO}}_4^{-}$ reduction reaction. Because charge goes from $\text{-1}\text{to +2}$ .

Option D is incorrect: ${\text{MnO}}_4^{-}$ is the oxidizing agent.